Rapid detection of microbial contamination in Ghanaian herbal medicines by PCR analysis

There is widespread use of herbal medicines across the world and the need for regulatory measures to ensure their safety, efficacy and quality is therefore imperative. Conventional microbiological methods are used in carrying out quality control analysis of herbal medicines but these are often slow, may be less sensitive or specific and labour-intensive. In this study we investigated the ability to use Polymerase Chain Reaction (PCR) as a fast, accurate and inexpensive novel method to detect the presence of common pathogens in herbal medicines from Ghana.

We employed different DNA extraction techniques including TE buffer, boiling method for DNA extraction as well as commercially available DNA extraction kits from Qiagen, UK: Gentra Pure-gene Yeast/Bact. Kit and DNeasy™ Tissue Kit which is column based to identify Escherichia coli, Staphylococcus aureus and Salmonella sp. in herbal products from Ghana in local African shops on the UK market.

The TE buffer and boiling methods did not yield any bacterial DNA, however both commercial kits yielded significant amounts of DNA. PCR was able to detect pathogens present in the samples directly. Escherichia coli could be detected at 10 cfu/ml whilst Staphylococcus aureus was detectable at a threshold of up to 10(3) cfu/ml when samples were enriched overnight. Salmonella sp. could not be detected in DNA samples extracted from herbal medicines.

We conclude that PCR and similar new molecular techniques such as Real Time PCR have the potential as rapid microbiological analytical techniques especially in busy clinical settings and for quality control of herbal medicines.